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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/files/important_file_writer.h"
#include <stdio.h>
#include <string>
#include "base/bind.h"
#include "base/critical_closure.h"
#include "base/file_util.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "base/logging.h"
#include "base/metrics/histogram.h"
#include "base/strings/string_number_conversions.h"
#include "base/task_runner.h"
#include "base/task_runner_util.h"
#include "base/threading/thread.h"
#include "base/time/time.h"
namespace base {
namespace {
const int kDefaultCommitIntervalMs = 10000;
enum TempFileFailure {
FAILED_CREATING,
FAILED_OPENING,
FAILED_CLOSING,
FAILED_WRITING,
FAILED_RENAMING,
TEMP_FILE_FAILURE_MAX
};
void LogFailure(const FilePath& path, TempFileFailure failure_code,
const std::string& message) {
UMA_HISTOGRAM_ENUMERATION("ImportantFile.TempFileFailures", failure_code,
TEMP_FILE_FAILURE_MAX);
DPLOG(WARNING) << "temp file failure: " << path.value().c_str()
<< " : " << message;
}
} // namespace
// static
bool ImportantFileWriter::WriteFileAtomically(const FilePath& path,
const std::string& data) {
// Write the data to a temp file then rename to avoid data loss if we crash
// while writing the file. Ensure that the temp file is on the same volume
// as target file, so it can be moved in one step, and that the temp file
// is securely created.
FilePath tmp_file_path;
if (!base::CreateTemporaryFileInDir(path.DirName(), &tmp_file_path)) {
LogFailure(path, FAILED_CREATING, "could not create temporary file");
return false;
}
File tmp_file(tmp_file_path, File::FLAG_OPEN | File::FLAG_WRITE);
if (!tmp_file.IsValid()) {
LogFailure(path, FAILED_OPENING, "could not open temporary file");
return false;
}
// If this happens in the wild something really bad is going on.
CHECK_LE(data.length(), static_cast<size_t>(kint32max));
int bytes_written = tmp_file.Write(0, data.data(),
static_cast<int>(data.length()));
tmp_file.Flush(); // Ignore return value.
tmp_file.Close();
if (bytes_written < static_cast<int>(data.length())) {
LogFailure(path, FAILED_WRITING, "error writing, bytes_written=" +
IntToString(bytes_written));
base::DeleteFile(tmp_file_path, false);
return false;
}
if (!base::ReplaceFile(tmp_file_path, path, NULL)) {
LogFailure(path, FAILED_RENAMING, "could not rename temporary file");
base::DeleteFile(tmp_file_path, false);
return false;
}
return true;
}
ImportantFileWriter::ImportantFileWriter(const FilePath& path,
base::SequencedTaskRunner* task_runner)
: path_(path),
task_runner_(task_runner),
serializer_(NULL),
commit_interval_(TimeDelta::FromMilliseconds(kDefaultCommitIntervalMs)),
weak_factory_(this) {
DCHECK(CalledOnValidThread());
DCHECK(task_runner_.get());
}
ImportantFileWriter::~ImportantFileWriter() {
// We're usually a member variable of some other object, which also tends
// to be our serializer. It may not be safe to call back to the parent object
// being destructed.
DCHECK(!HasPendingWrite());
}
bool ImportantFileWriter::HasPendingWrite() const {
DCHECK(CalledOnValidThread());
return timer_.IsRunning();
}
void ImportantFileWriter::WriteNow(const std::string& data) {
DCHECK(CalledOnValidThread());
if (data.length() > static_cast<size_t>(kint32max)) {
NOTREACHED();
return;
}
if (HasPendingWrite())
timer_.Stop();
if (!PostWriteTask(data)) {
// Posting the task to background message loop is not expected
// to fail, but if it does, avoid losing data and just hit the disk
// on the current thread.
NOTREACHED();
WriteFileAtomically(path_, data);
}
}
void ImportantFileWriter::ScheduleWrite(DataSerializer* serializer) {
DCHECK(CalledOnValidThread());
DCHECK(serializer);
serializer_ = serializer;
if (!timer_.IsRunning()) {
timer_.Start(FROM_HERE, commit_interval_, this,
&ImportantFileWriter::DoScheduledWrite);
}
}
void ImportantFileWriter::DoScheduledWrite() {
DCHECK(serializer_);
std::string data;
if (serializer_->SerializeData(&data)) {
WriteNow(data);
} else {
DLOG(WARNING) << "failed to serialize data to be saved in "
<< path_.value().c_str();
}
serializer_ = NULL;
}
void ImportantFileWriter::RegisterOnNextSuccessfulWriteCallback(
const base::Closure& on_next_successful_write) {
DCHECK(on_next_successful_write_.is_null());
on_next_successful_write_ = on_next_successful_write;
}
bool ImportantFileWriter::PostWriteTask(const std::string& data) {
// TODO(gab): This code could always use PostTaskAndReplyWithResult and let
// ForwardSuccessfulWrite() no-op if |on_next_successful_write_| is null, but
// PostTaskAndReply causes memory leaks in tests (crbug.com/371974) and
// suppressing all of those is unrealistic hence we avoid most of them by
// using PostTask() in the typical scenario below.
if (!on_next_successful_write_.is_null()) {
return base::PostTaskAndReplyWithResult(
task_runner_,
FROM_HERE,
MakeCriticalClosure(
Bind(&ImportantFileWriter::WriteFileAtomically, path_, data)),
Bind(&ImportantFileWriter::ForwardSuccessfulWrite,
weak_factory_.GetWeakPtr()));
}
return task_runner_->PostTask(
FROM_HERE,
MakeCriticalClosure(
Bind(IgnoreResult(&ImportantFileWriter::WriteFileAtomically),
path_, data)));
}
void ImportantFileWriter::ForwardSuccessfulWrite(bool result) {
DCHECK(CalledOnValidThread());
if (result && !on_next_successful_write_.is_null()) {
on_next_successful_write_.Run();
on_next_successful_write_.Reset();
}
}
} // namespace base
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